1. Field of the Invention
The present invention relates to a friction material, and more particularly, it relates to a friction material which is optimum for a sliding surface of a brake lining, a disc pad, a clutch facing or the like in a braking system of an automobile, rolling stock, an aircraft, an industrial machine or the like.
2. Description of the Prior Art
A friction material prepared by dispersing a base material in a binder of resin such as phenolic resin or epoxy resin, adding a friction conditioner as needed and binding and molding the mixture under heat and pressure is known for use as a friction material in the aforementioned braking system.
The friction coefficient of such a friction material is generally reduced as the temperature is increased. When an automobile continuously goes down descents or the like, therefore, the braking performance is remarkably reduced through so-called fading as the friction material becomes frictionally heated. To this end, a friction material employed under a high load condition is prepared from a sintered alloy based on a metal such as copper with addition of a friction conditioner such as graphite or ceramics in recent years.
However, some conventional friction material of a sintered alloy (hereinafter referred to as a sintered friction material) is insufficient in lubricity and remarkably abrades the counterpart although the friction material itself is less abraded. Another conventional friction material is remarkably abraded itself, although it abrades the counterpart to a larger degree. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
Still another conventional sintered friction material is insufficient in lubricity and remarkably abrades the counterpart although it exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although it abrades the counterpart to a larger degree. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in material strength although the same exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although the same is sufficient in material strength. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in judder resistance or chatter resistance although the friction material itself is less abraded. A further friction material is remarkably abraded itself although the same is sufficient in judder resistance. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.
A further conventional sintered friction material is insufficient in creak resistance or squealing resistance although the same exhibits a high friction coefficient. A further friction material is remarkably reduced in friction coefficient although the same is sufficient in creak resistance. Thus, these conventional sintered friction materials have unsatisfactory characteristics under the present circumstances.